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Fri, 20 Jun 2025 13:27:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id pBhfDL9hVWiXOQAAD6G6ig (envelope-from ); Fri, 20 Jun 2025 13:27:27 +0000 Date: Fri, 20 Jun 2025 15:27:25 +0200 From: Oscar Salvador To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato Subject: Re: [PATCH RFC 03/14] mm: compare pfns only if the entry is present when inserting pfns/pages Message-ID: References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-4-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250617154345.2494405-4-david@redhat.com> X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[29]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_RATELIMIT(0.00)[to_ip_from(RL88oxspsx4bg3gu1yybyqiqt4)]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Queue-Id: C703C1F38D X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: -4.51 On Tue, Jun 17, 2025 at 05:43:34PM +0200, David Hildenbrand wrote: > Doing a pte_pfn() etc. of something that is not a present page table > entry is wrong. Let's check in all relevant cases where we want to > upgrade write permissions when inserting pfns/pages whether the entry > is actually present. Maybe I would add that's because the pte can have other info like marker, swp_entry etc. > It's not expected to have caused real harm in practice, so this is more a > cleanup than a fix for something that would likely trigger in some > weird circumstances. > > At some point, we should likely unify the two pte handling paths, > similar to how we did it for pmds/puds. > > Signed-off-by: David Hildenbrand Reviewed-by: Oscar Salvador Should we scream if someone passes us a non-present entry? > --- > mm/huge_memory.c | 4 ++-- > mm/memory.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 8e0e3cfd9f223..e52360df87d15 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1392,7 +1392,7 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr, > const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) : > fop.pfn; > > - if (write) { > + if (write && pmd_present(*pmd)) { > if (pmd_pfn(*pmd) != pfn) { > WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); > return -EEXIST; > @@ -1541,7 +1541,7 @@ static void insert_pud(struct vm_area_struct *vma, unsigned long addr, > const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) : > fop.pfn; > > - if (write) { > + if (write && pud_present(*pud)) { > if (WARN_ON_ONCE(pud_pfn(*pud) != pfn)) > return; > entry = pud_mkyoung(*pud); > diff --git a/mm/memory.c b/mm/memory.c > index a1b5575db52ac..9a1acd057ce59 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2137,7 +2137,7 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte, > pte_t pteval = ptep_get(pte); > > if (!pte_none(pteval)) { > - if (!mkwrite) > + if (!mkwrite || !pte_present(pteval)) > return -EBUSY; Why EBUSY? because it might transitory? -- Oscar Salvador SUSE Labs